The High Energy X-ray Probe (HEX-P): Studying Extreme Accretion with Ultraluminous X-ray Sources
Abstract
Ultraluminous X-ray sources (ULXs) represent an extreme class of accreting compact objects: from the identification of some of the accretors as neutron stars to the detection of powerful winds travelling at 0.1-0.2 c, the increasing evidence points towards ULXs harbouring stellar-mass compact objects undergoing highly super-Eddington accretion. Measuring their intrinsic properties, such as the accretion rate onto the compact object, the outflow rate, the masses of accretor/companion -- hence their progenitors, lifetimes, and future evolution -- is challenging due to ULXs being mostly extragalactic and in crowded fields. Yet ULXs represent our best opportunity to understand super-Eddington accretion physics and the paths through binary evolution to eventual double compact object binaries and gravitational wave sources. Through a combination of end-to-end and single-source simulations, we investigate the ability of HEX-P to study ULXs in the context of their host galaxies and compare it to XMM-Newton and NuSTAR, the current instruments with the most similar capabilities. HEX-P's higher sensitivity, which is driven by its narrow point-spread function and low background, allows it to detect pulsations and broad spectral features from ULXs better than XMM-Newton and NuSTAR. We describe the value of HEX-P in understanding ULXs and their associated key physics, through a combination of broadband sensitivity, timing resolution, and angular resolution, which make the mission ideal for pulsation detection and low-background, broadband spectral studies.
Keywords
Cite
@article{arxiv.2311.04733,
title = {The High Energy X-ray Probe (HEX-P): Studying Extreme Accretion with Ultraluminous X-ray Sources},
author = {Matteo Bachetti and Matthew J. Middleton and Ciro Pinto and Andrés Gúrpide and Dominic J. Walton and Murray Brightman and Bret Lehmer and Timothy P. Roberts and Georgios Vasilopoulos and Jason Alford and Roberta Amato and Elena Ambrosi and Lixin Dai and Hannah P. Earnshaw and Hamza El Byad and Javier A. García and Gian Luca Israel and Amruta Jaodand and Kristin Madsen and Chandreyee Maitra and Shifra Mandel and Kaya Mori and Fabio Pintore and Ken Ohsuga and Maura Pilia and Daniel Stern and George Younes and Anna Wolter},
journal= {arXiv preprint arXiv:2311.04733},
year = {2023}
}
Comments
24 pages, 9 figures. Accepted for publication in Frontiers of Astronomy and Space Science. Minor corrections included